I have a 97 4x4 with the 4.6 engine. Here is what has got me stumped. Truck cranks but wont start so I replaced fuel pump and filter, new plugs and wires. Checked spark looks good checked fuel injectors with noid light all working. Fuel pressure goes up to 35psi when I turn key on.When I start cranking the motor the fuel pressure goes to zero and does not come back until I cycle ignition swich again. Checked relay and fuse to fuel pump both good. Am I looking at a PCM?

 

Look for the crank position sensor signal first.

 

When you say look for crank position signal first I am confused. I thought that if you had spark your sensor was good? Where else do I need to look?
Thanks

 

I think the issue is more likely a bad ignition switch.